1. Field of the Invention
The present invention relates to an interlock device for turning ON a power source of a device housed within a casing when both of hinged double doors are closed.
2. Description of the Related Art
Many apparatuses, such as control panels and so on, are housed within a housing with a door. When the apparatus is in operation, the door of the casing is held closed. Upon maintenance and inspection of the apparatus and replacement of consumable articles and so forth, the power supply is turned OFF and the door is opened to perform necessary operation. In such apparatus, in order to avoid the occurrence of a misstep of turning ON the power supply while the door is held open or the misstep of opening the door while the apparatus is in operation, an interlock device for enabling power supply to the apparatus only when the door is closed, is provided. The interlock device is provided with an interlock switch (hereinafter simply referred to as switch). The switch is held ON while the door is held closed, for enabling power supply to the apparatus.
On the other hand, among various casings, there are some casings of the type having two doors for one opening, such as a hinged double door, for example. The casing of this type is advantageous due to the motion area of the door in comparison with the size of the opening portion.
However, such prior art encounters the following problems. In the case of the method providing the switch per the door, the number of switches is increased to make a cost of the interlock device higher. As a result, the cost of the overall apparatus, such as a control panel or so forth, is significantly influenced.
On the other hand, in the case of the method providing only one switch for one of the doors, the power may be supplied while the door provided with the switch is closed, irrespective of the position of other doors. Thus, such an approach encounters a problem from the viewpoint of security.
The present invention has been worked out in view of the drawbacks set forth above. It is an object of the present invention to provide an interlock device for a casing of double door structure, which can enable a power supply with one switch only when both doors are closed.
According to one aspect of the present invention, an interlock device applicable for a casing having an opening opened and closed by a first door and a second door in hinged double door construction for supplying power to an apparatus housed within the casing when both of the first door and the second door are closed, comprises:
a lever pivotably supported at an intermediate portion and being pivoted in a predetermined direction as pushed one end portion by the first door when the first door is closed;
a link member responsive to pivot motion of the lever to the predetermined position and driven by the other end of the lever to be moved from a first position on the side of the first door to a second position on the side of the second door;
a pushing member mounted on the link member and responsive to closure of the second door while the link member is placed at the second position, to be pushed into a third position; and
a switch responsive to the pushing member placed at the third position to turn ON power supply for the apparatus.
As set forth above, in the present invention, the link member is moved from the first position to the second position by closing the first door. Then, by closing the second door, the pushing member is pushed into the third position to turn the switch ON by the pushing member. Thus, with one switch, the power is supplied to the apparatus only when both of the first and second doors are closed.
In the preferred construction, the pushing member may be mounted on the link member in such a manner that a direction of movement (e.g., pushing) intersects with moving direction of the link member.
On the other hand, the pushing member may be constantly placed at a fourth position and may be pushed to move when the second door is closed, and a first resilient member biasing the pushing member toward the fourth position may be provided between the link member and the pushing member.
Also, the first and second doors may be pivoted about horizontal shafts, the opening portion may be arranged at the front side of the casing, and the lever may be pivotable about a horizontal shaft, the first position may be arranged lower than the second position, and the link member may be constantly biased toward the first position by gravity.
The interlock device may further comprise a second resilient member provided between the casing and the link member and constantly biasing the link member toward the first position.
Preferably, the lever may be bent at a pivot portion pivotably supported on the horizontal shaft so that one portion and the other portion extend in mutually different directions, and side edges of the one portion and the other portion to be pushed by the first door intersect at an angle greater than 180xc2x0.